Simultaneous sum and difference pattern technique for circular array antennas

ABSTRACT

Apparatus for obtaining simultaneous sum and difference patterns with a circular-array antenna fed by an R-2R parallel-plate lens systems. The apparatus comprises sum and difference circuits which in combination with switching circuitry can provide a plurality of different combinations of amplitude taper to a multiple input/output port lens system to achieve 360* scan from an array antenna fed thereby. A sum power divider and a difference power divider are connected directly and through 180* hybrid couplers respectively, to one side of a DPDT, amplitude pass-around switch to provide selectively predetermined combinations of the outputs of the two power dividers. The resulting combinations are fed to the ports of the lens system in a conventional manner. The sum pattern is used for transmission, and both the sum and difference patterns are used on reception.

ited States Patent [191 oyns [75] inventor: Jerry E. Boyns, San Diego, Calif.

[73] Assignee: The United States of America as represented by the Secretary of the Navy [22] Filed: Aug. 14, 1972 [211 App]. No.2 280,627

[52] US. Cl ..343/854, 333/7 [5 l 1 Int. Cl. ..H0lq 3/26 [58] Field of Search ..343/754, 778, 854;

[56] References Cited UNITED STATES PATENTS 3,573,837 4/197] Reindel..... ..343/778 SENDER APPARATUS POWER DIVIDE R POWER /2 DIV/DER 3,729,742 Apr. 24, 1973 [57] ABSTRACT Apparatus for obtaining simultaneous sum and difference patterns with a circular-array antenna fed by an R-2R parallel-plate lens systems. The apparatus comprises sum and difference circuits which in comhination with switching circuitry can provide a plurality of different combinations of amplitude taper to a multiple input/output port lens system to achieve 360 scan from an array antenna fed thereby. A sum power divider and a difi'erence power divider are connected directly and through 180 hybrid couplers respectively, to one side of a DPDT, amplitude pass-around switch to provide selectively predetermined combina tions of the outputs of the two power dividers. The resulting combinations are fed to the ports of the lens system in a conventional manner. The sum pattern is used for transmission, and both the sum and difference patterns are used on reception.

6 Claims, 2 Drawing Figures ARRAY ANTENNA Patented" A ril 24, 1973 2 Sheets-Sheet 2 RELATIVE POWER ONE WAY (dB) BACKGROUND OF THE INVENTION U. S. Pat. No. 3,568,207, entitled Parallel Plate Feed System for a Circular Array Antenna by Jerry E. Boyns et al., disclosed a feed system for a circular array antenna wherein the array comprises a plurality of radiating elements embedded along the circumference of a metallic cylinder of radius 2R. The parallel-plate region comprises two circular metal plates of radius R having a number of input/output ports equi-spaced along the circumference of the region and is fed by simultaneously exciting with a tapered amplitude distribution a plurality of input ports positioned adjacent to each other. The distribution which results at the output ports has a considerable taper, and if applied to array radiating elements with proper phase from the parallel-plate region, low-sidelobe patterns can be obtained. Selectively predetermined numbers of input/output ports can be selected to obtain the amplitude and phase distribution required for a'given antenna beam.

Prior-art array techniques which employed R-2R lens feed approaches used only a single input/output lens system and thus could not be used to produce simultaneous sum and difference patterns. The technique disclosed in the above-referenced patent, on the other hand, due to its multiple input/output probe capability can be used to produce the above patterns in accordance with the inventive concept to be disclosed herein.

SUMMARYOF THE INVENTION Apparatus are disclosed for enabling a circular array antenna fed with an R-2R parallel-plate system to radiate multiple beams whereby a sum beam searches for targets while a difference beam precisely locates a target previously located by the sum beam. The apparatus comprises a sum channel which is used for transmitting and receiving and a difference channel which is used for receiving. The two channels combine with switching circuitry to provide four different corn binations of amplitude distribution to achieve stepping of a beam around the circular array. A sum power divider and a difference power divider are connected directly and through I80 hybrid couplers, respectively, to one side of a DPDT amplitude pass-around switch. The junction of the power dividers comprises magic tees to provide isolation between the two dividers. The difference circuit provides a tapered input and an untapered input to the lens; the two inputs are adjacent and are shifted l80 with respect to the other two inputs. The opposite side of the switch is connected to conventional switching apparatus which couples the amplitude distribution to selectively predetermined input ports of the R-2R parallel-plate to feed the circular array as above to produce simultaneous sum and difference patterns.

STATEMENT OF THE OBJECTS OF INVENTION The primary object of the inventive concept disclosed herein is to achieve multiple beam radiation from a circular array whereby a sum beam searches for targets while a difference beam precisely locates a target previously located by the sum beam.

It is another object to substantially increase the operational capabilities of circular array antennas fed by R-2R lens systems as disclosed in U. S. Pat. No. 3,568,207.

Other objects, advantages and novel features of the invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a simplified block diagram illustration of a system embodying the present inventive concept for use with a circular array antenna fed by an R-ZR lens system to achieve simultaneous sum and difference patterns by the radiation of multiple beams.

FIG. 2 is a simplified, exemplary graphical illustration of a simultaneous sum and difference pattern obtained in accordance with the concept disclosed herein.

DESCRIPTION OF THE PREFERRED EMBODIMENT As mentioned previously, U. S. Pat. No. 3,568,207 disclosed apparatus for feeding a circular array antenna to produce low-sidelobe patterns. The array shown therein is fed by means of a parallel-plate region consisting of two metal plates having a plurality of input/output ports equi-spaced along the circumference thereof. The plates are spaced apart less than one-half a free-space wavelength so that only the electric field component perpendicular to the plates is propagated. Energy is launched and extracted from the lens by monopoles mounted one-quarter wavelength in front of the circumferential ground plane which encloses the lens.

The apparatus and techniques to be described hereinafter extend the operational capabilities of the above circular array antenna by providing for the radiation of multiple beams whereby simultaneous sum and difference pattern reception is achieved.

FIG. 1 illustrates in simplified block diagram form such apparatus operationally connected to the system of the above-referenced patent to achieve simultaneous sum and difference patterns from a ring array excited by an R-2R lens. To simplify the discussion of the inventive concept the exemplary circular array illustrated in the referenced patent is used in FIG. 1 and herein. Thus the array to be discussed comprises a l28-element array excited by a 64-port, R-2R lens system, however it should be appreciated that the inventive concept could be practiced with any even-number element array having one-half that number of ports.

In FIG. 1 of the present disclosure, microwave energy sender apparatus which can be either transmitting or receiving means, is connected to the input of the two power dividers l2 and 14. The dividers l2 and 14 are in what will hereinafter be referred to as the sum and difference channels, respectively. The sum power divider 14 in the first channel has a power ratio of, for example, 1:4, and its output comprises four distinct amplitudes: X, l, l, and X. The output is connected to the DPDT amplitude pass-around switch 16. As will be seen later, the sum pattern is used only for transmission.

The power divider 12 has a power ratio of, for example, 1:2 and its output comprises two distinct amplitudes: X and l. The output is also connected to the pass-around switch 16; however, it is first passed through the two 180 hybrid couplers 20 and 22 to produce the output comprising four distinct amplitude levels: Xti), X, l, 14). As can be seen, the hybrid couplers provide 180 phase shift between the sum and difference channels and the power divider 12. The difference and sum patterns are both used for reception.

The junctions of the outputs of the power divider circuits comprise magic tee waveguide connectors 24 which function to isolate the two outputs from each other thereby minimizing interaction and allowing both channels to be available simultaneously.

The switch 16 is in series with a conventional switching network 18 comprising four, single-pole, sixteen-throw switches A, B, C, and D. The connections from the switch assembly 18 to the parallel-plate 26 are identical to the connections shown in the referenced patent wherein the output thereof is connected to the input/output ports 28 along the circumference of the parallel-plate region which feeds a l28-element circular array (not shown). Connected to each input/output port 28 is a SP4T diode switch 30 as shown in the referenced patent for achieving 360 scan. Equallength cables 32 couple the output of the switch 30 to the radiating elements on the circular array.

The columns in the two tables shown in FIG. 1 represent the different combinations of amplitude distribution which are produced by the sum and difference circuits and which are required to achieve 360 scan or stepping of the beam around the circular array. The amplitudes are achieved by positioning the switch 16 arms 2, 3, 4, and 5, to various contact positions. For example, the sum channel will produce the amplitude distribution X, l, l, X, if the arms 2, 3, 4, and are in the positions shown in FIG. 1. The receive channel will produce the distribution X, l, 14), Xgb. If the arms 2 and 3 are positioned in contact with contacts e and f, respectively, and 4 and 5 remain as in FIG. 1, the sum channel will produce X, X, l, 1, while the difference channel will produce X, X4), 1d), 1.

The remaining columns in the two tables are obtained in a like manner. As can be seen from the difference table, one tapered and one untapered input from the difference circuit to the plate 26 must be adjacent and shifted in phase by 180 with respect to the other two inputs.

As stated above, four separate beam positions can be achieved. Thus the four tapers available at the output of the amplitude pass-around switch 16 can produce 64 beam positions by the switching action provided by the switch assembly 18. The use of SP4T switches 30 at each input/output port allows the l28-beam positions required by the l 28-element circular array.

It can be appreciated that novel apparatus and techniques have been described for multiple beam radiation by circular array antennas fed by R-ZR parallel-plate devices. The concept disclosed makes possible simultaneous reception of sum and difference patterns whereby a sum beam can search for targets while a difference beam can precisely locate a target previously located by the sum beam.

It should be understood and appreciated that the novel technique could be used advantageously with an array having almost any even number of elements and with a lens system having one-half that number of ports. For example, an array with 64-elements and a lens system with 32-ports would be possible if SP8T switches were used in lieu of SP16T switches. if its SlPl6T switches are not used, an eight-element array could be used with a four-port lens system to achieve the sum and difference pattern desired.

Furthermore, the power ratio of the power dividers can be selectively predetermined as a function of the power or amplitude taper desired to produce low sidelobes. If low sidelobes are not required, the power ratio could be lzl.

Obviously many modifications and variations of the present invention are possible in the light of the above teachings. It is therefore to be understood that within the scope of the appended claims the invention may be practiced otherwise than as specifically described.

What is claimed is:

1. Apparatus for obtaining simultaneous sum and difference patterns from a circular-array antenna fed by a multiport, parallel-plate lens system comprising:

sender apparatus for transmitting energy to and receiving energy from said antenna; first channel means connected to said sender apparatus for providing a selectively predetermined sum signal comprising a first plurality of distinct amplitude levels to be transmitted or received therefrom; second channel means connected to said sender apparatus for providing a selectively predetermined difference signal comprising a second plurality of distinct amplitude levels to be received therefrom;

switch means connected to said first and second channel means for simultaneously providing a first selectively predetermined combinations of said first amplitude levels for transmission by said sender apparatus and a second selectively predetermined combination of said first and second amplitude levels for transmission and reception by said sender apparatus;

means for phase shifting said difference signal a selectively predetermined amount with respect to said sum signal;

means for providing microwave energy isolation between said first and second power divider means to prevent interaction between said sum signal and said difference signal; and,

means for simultaneously coupling energy between said switch means and said antenna during transmission and reception.

2. The apparatus of claim 1 wherein said first channel means includes a first power divider and said second channel means includes a second power divider, said power divider having selectively predetermined power ratios different with respect to each other.

3. The apparatus of claim 1 wherein said means for phase shifting said difference signal comprises hybrid coupler means.

4. The apparatus of claim 1 wherein said means for providing isolation comprises magic tees.

5. The apparatus of claim 1 wherein said switch means comprises an amplitude pass-around switch.

6. Apparatus for obtaining multiple-beam radiation from a l28-element, circular-array antenna fed with a 64-port, R-2R, parallel plate lens system comprising:

reciprocal, microwave energy sender apparatus;

first power divider means connected to said Sender apparatus and having a 1:4 power ratio whereby four distinct amplitude levels are produced at the output thereof;

reciprocal amplitude pass-around switch means connected to said first power divider means,

said switch means comprising double-pole, doublethrow switch means having four inputs and four corresponding outputs and adapted to receive at each input a different one of said amplitude levels to produce at said four outputs selectively predetermined combinations of said amplitude levels;

single-pole, sixteen-throw switch means connected to each of said four outputs to couple in a selectively predetermined manner said combinations of said amplitude levels to said parallel-plate to be fed therefrom to said antenna;

said single-pole, l6-throw switch means further being adapted to receive energy from said antenna and to couple received energy as four distinct received amplitude levels to said four output terminals of said amplitude pass-around switch means;

said switch means being adapted to produce at the input thereof selectively predetermined combinations of said four received amplitude levels corresponding to said selectively predetermined combinations fed to said antenna in a transmit mode;

second power divider means connected to said sender means and having a 1:2 power ratio;

hybrid coupler means connected to said second power divider means at the opposite side thereof and having four input terminals,

each of said input terminals being connected to a different one of said four inputs of said switch means whereby said coupler means receives said selectively predetermined combinations of said four received amplitude levels; and,

microwave energy isolation means connected at each of the four junctions of said four amplitude levels from said first power divider means and said selectively predetermined combination of said four received amplitude levels to prevent interaction therebetween and to allow simultaneous transmission and reception thereof, respectively. 

1. Apparatus for obtaining simultaneous sum and difference patterns from a circular-array antenna fed by a multiport, parallel-plate lens system comprising: sender apparatus for transmitting energy to and receiving energy from said antenna; first channel means connected to said sender apparatus for providing a selectively predetermined sum signal comprising a first plurality of distinct amplitude levels to be transmitted or received therefrom; second channel means connected to said sender apparatus for providing a selectively predetermined difference signal comprising a second plurality of distinct amplitude levels to be received therefrom; switch means connected to said first and second channel means for simultaneously providing a first selectively predetermined combinations of said first amplitude levels for transmission by said sender apparatus and a second selectively predetermined combination of said first and second amplitude levels for transmission and reception by said sender apparatus; means for phase shifting said difference signal a selectively predetermined amount with respect to said sum signal; means for providing microwave energy isolation between said first and second power divider means to prevent interaction between said sum signal and said difference signal; and, means for simultaneously coupling energy between said switch means and said antenna during transmission and reception.
 2. The apparatus of claim 1 wherein said first channel means includes a first power divider and said second channel means includes a second power divider, said power divider having selectively predetermined power ratios different with respect to each other.
 3. The apparatus of claim 1 wherein said means for phase shifting said difference signal comprises hybrid coupler means.
 4. The apparatus of claim 1 wherein said means for providing isolation comprises magic tees.
 5. The apparatus of claim 1 wherein said switch means comprises an amplitude pass-around switch.
 6. Apparatus for obtaining multiple-beam radiation from a 128-element, circular-array antenna fed with a 64-port, R-2R, parallel plate lens system comprising: reciprocal, microwave energy sender apparatus; first power divider means connected to said sender apparatus and having a 1:4 power ratio whereby four distinct amplitude levels are produced at the output thereof; reciprocal amplitude pass-around switch means connected to said first power divider means, said switch means comprising double-pole, double-throw switch means having four inputs and four corresponding outputs and adapted to receive at each input a different one of said amplitude levels to produce at said four outputs selectively predetermined combinations of said amplitude levels; single-pole, sixteen-throw switch means connected to each of said four outputs to couple in a selectively predetermined manner said combinations of said amplitude levels to said parallel-plate to be fed therefrom to said antenna; said single-pole, 16-throw switch means further being adapted to receive energy from said antenna and to couple received energy as four distinct received amplitude levels to said four output terminals of said amplitude pass-around switch means; said switch means being adapted to produce at the input thereof selectively predetermined combinations of said four received amplitude levels corresponding to said selectively predetermined combinations fed to said antenna in a transmit mode; second power divider means connected to said sender means and having a 1:2 power ratio; 180* hybrid coupler means connected to said second power divider means at the opposite side thereof and having four input terminals, each of said input terminals being connected to a different one of said four inputs of said switch means whereby said coupler means receives said selectively predetermined combinations of said four received amplitude levels; and, microwave energy isolation means connected at each of the four junctions of said four amplitude levels from said first power divider means and said selectively predetermined combination of said four received amplitude levels to prevent interaction therebetween and to allow simultaneous transmission and reception thereof, respectively. 